If you look at the top of this (and every page on this site) there is a link called "[url=http://manual.b2evolution.net/]Docs[/url]"... Follow that link and read every link under the section titled "The Backoffice".

Among those links you'll find this information:

Next you'll see the "Post contents" section. The first field is for your post title. The field below that is labeled "Link to url:". You can add a web address here (don't forget the http://) and in your blog, the post title will become a link to this url. This is especially useful in a Linkblog, but it can and most often is left blank.

I found that by following the link titled [url=http://manual.b2evolution.net/Write_tab]The Write Tab[/url].

Lower on that same page, you'll find this text:

You can also edit the url title, which is part of the permanent link for this post. The url title is normally created automatically by b2evolution. The software takes your post title, shortens it if it's too long and converts special characters (including spaces) to underscores. Normally, leave this field blank, but if you need to, you can specify or edit your url title here.

which answers your second question.

By using the [url=http://forums.b2evolution.net/search.php]Search Function[/url], also at the top of every page on this site, and entering the search words:
what are trackbacks
I found [url=http://forums.b2evolution.net/viewtopic.php?t=12247&highlight=trackbacks]this post[/url], which was made 4 days ago, in which Afwas said:

When I read one of your posts, I might consider commenting on that. I can do so on your blog, but I could also write in my own blog. In that case I have the option to trackback you and if your blog enables it, it displays a link to my blog. This way my article (a comment on your blog) is visible to both my viewers and yours. This will often be interesting if we both blog about the same topics, say gadgets or cooking.

On that page you'll also find a link to yet another page that provides even more info about trackbacks.

jj.

Thanks for your reply. I have read all that but maybe I cant understand it. Anyway, please tell me what will happen if I leave them blank.

ok now everybody can say im so dumb and ill accept it unhurtingly but pls tell me and answer me in simple common words, keeping in your mind that im dumb.

what is "link to url", "url title" and "trackback urls" on the write tab in the admin?

does it mean that if i put "http://domain.com/post_title" to "link to url", the post title will have link like this? and/or everytime you go to http://domain.com/post_title, you will be directed to this post "post_title"?

what's the use of "link to url"?

url title: i know that b2e automatically assigns the title of the post to it, but what's its use?

trackback url: i know what its for as above posts explain but should i leave it blank bcoz my post is original and doesnt talk about other post to other blogs or should i put a link if im talking about or commenting something about other posts or other blogs? pls explain in a very simple way. if you can give me an example to make me understand, pls do so. thank you.