One-way link is getting a backlink from a website. For an example, you go to a bookmark site and bookmark your website. You can see a link from that particular bookmark site. That is called one-way link building, there are various methods, you can learn more on this forum.

It's pretty much what it sounds like. A link from one website to another.
In contrast you would get a reciprocal link which would be when you have two websites that each link to each other.
In my opinion this is not advisable though as it looks unnatural if it occurs too often.

I am working with articles, blog commenting, forum posting and classified ads. All these activities help for getting useful one way link for the website. By this process your one way link always live.

Forum posting? Will the forum posts in this forum help by having backlinks in your signature?

One way link means you need not to follow their website. Simply they give you a back link without expecting any thing from you.

Direct link to your money site..

A "one-way text link" means that a Web site links to your Web site but you don’t link back to that Web site. One-way links, also known as non-reciprocal links, are much more difficult to obtain than traditional reciprocal links. In the eyes of search engines, one-way text links have a more natural flow and appear less self-serving. As a result, they are very valuable to your business because the more one-way links you have, the better your chances of an improved search engine ranking, page rank and link popularity.

One way link: site links to you. (Best)

Reciprocal link: site links and you link back. (Still pretty good)

[DELETED]

It links to you - you DON'T link back = one way link.