Here are two basic definitions which I find helps someone new to the “marketing themselves” world:

BLOG
Short for “web log”: a discussion or information site published on the Internet consisting of entries (posts) typically displayed in reverse chronological order so the most recent post appears first.

Originally mostly used as a sort of public diary where people would post their own personal rants (and commonly known to NOT be easy to read with posts full of grammatical errors). It has since become a PR and marketing tool for companies, brands and individuals by providing information that they hope their public would be interested in.

Although not a must, most good quality blogs are interactive, allowing visitors to leave comments and even message each other via the blogs. It is this interactivity that distinguishes them from other “static” websites. In that sense, blogging can be seen as a form of social networking.

SOCIAL NETWORKING
A social networking service is an online service, platform, or site that focuses on giving you the opportunity to build networks/relationships with other people. For the most part these other people share interests, activities, background or real-life connections with you.

A social network service consists of a representation of each user (often a profile), his/her social links, information about you and a variety of additional services. Most social network services are web-based and provide means for users to interact over the Internet, such as e-mail, instant messaging, games, forums, etc.

Social networking sites allow users to share ideas, activities, events and interests within their individual networks.

Each one is like a party or gathering that you go to and interact with the other people who have shown up at the party.

Feel free to email me any other concepts or words you would like me to help you understand.