The Internet:
The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked Web pages and other documents of the World Wide Web.

A Website:
A website (alternatively, Web site or web site) is a collection of Web pages, images, videos and other digital assets that is hosted on one or several Web server(s), usually accessible via the Internet, cell phone or a LAN. A Web page is a document, typically written in HTML, that is almost always accessible via HTTP, a protocol that transfers information from the Web server to display in the user's Web browser. All publicly accessible websites are seen collectively as constituting the "World Wide Web". The pages of websites can usually be accessed from a common root URL called the homepage, and usually reside on the same physical server. The URLs of the pages organize them into a hierarchy, although the hyperlinks between them control how the reader perceives the overall structure and how the traffic flows between the different parts of the sites.

Search Engine:
A search engine is an information retrieval system designed to help find information stored on a computer system, such as on the World Wide Web, inside a corporate or proprietary network, or in a personal computer. The search engine allows one to ask for content meeting specific criteria (typically those containing a given word or phrase) and retrieves a list of items that match those criteria. This list is often sorted with respect to some measure of relevance of the results. Search engines use regularly updated indexes to operate quickly and efficiently.

Internet Marketing:
Internet marketing, also referred to as Online Marketing, is Marketing that uses the Internet. The Internet has brought many unique benefits to marketing that include very low costs in distributing information and media to a global audience. However, the interactive nature of the media, both in terms of instant response, and in eliciting response at all, are both desirable qualities of internet marketing. Internet marketing ties together both the creative and technical aspects of the internet, including design, development, advertising and sales. Internet Marketing methods include search engine marketing, display advertising, e-mail marketing, affiliate marketing, interactive advertising and viral marketing.
 
Search Engine Marketing (SEM):
Search Engine Marketing, or SEM, is a form of Internet Marketing that seeks to promote websites by increasing their visibility in the Search Engine results pages (SERPs) and has a proven ROI (Return on Investment). According to the Search Engine Marketing Professionals Organization, SEM methods include: Search Engine Optimization (or SEO), paid placement, and paid inclusion.

Search Engine Optimisation (SEO):
Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via "natural" ("organic" or "algorithmic") search results. Usually, the earlier a site is presented in the search results, or the higher it "ranks", the more searchers will visit that site. SEO can also target different kinds of search, including image search, local search, and industry-specific vertical search engines.

Pay Per Click (PPC):
Pay per click (PPC) is an advertising model used on websites, advertising networks, and search engines where advertisers only pay when a user actually clicks on an ad to visit the advertiser's website. Advertisers bid on keywords they believe their target market would type in the search bar when they are looking for a product or service.

Google:
Google Inc is an American public corporation, specializing in Internet search and online advertising.

Google AdSense:
AdSense has become a popular method of placing advertising on a website because the ads are less intrusive than most banners, and the content of the ads is often relevant to the website.

Google AdWords:
AdWords is Google's flagship advertising product and main source of revenue. AdWords offers pay-per-click (PPC) advertising, and site-targeted advertising for both text and banner ads. The AdWords program includes local, national, and international distribution. Google's text advertisements are short, consisting of one title line and two content text lines. Image ads can be one of several different Interactive Advertising Bureau (IAB) standard sizes. Google

AdSense:
AdSense is an ad serving program run by Google. Website owners can enroll in this program to enable text, image and, more recently, video advertisements on their sites. These ads are administered by Google and generate revenue on either a per-click or per-thousand-impressions basis. Google is also currently beta-testing a cost-per-action based service.

Googlebot : A Googlebot is a search bot used by Google. It collects documents from the web to build a searchable index for the Google search engine. If a webmaster wishes to restrict the information on their site available to a Googlebot, or another well-behaved spider, they can do so with the appropriate directives in a robots.txt file.

Web Spider / Crawler:
A web crawler (also known as a Web spider or Web robot) is a program or automated script which browses the World Wide Web in a methodical, automated manner. Other less frequently used names for Web crawlers are ants, automatic indexers, bots, and worms (Kobayashi and Takeda, 2000). This process is called Web crawling or spidering

Source: www.wikipedia.com