Signatures are links to your own blog or website that make it easy for people to re-visit you after you comment on their blog. If you don't have one, people have to click on your name, and that either takes them to your Google+ profile, or your Blogger profile (or nowhere at all).
Is that a bad thing?
Well, if you are like me, and have multiple blogs (and not all of them are in the Challenge), there is nothing telling people on your Blogger profile what they should be clicking on. If you don't share your posts on G+, once again, it seems like a dead end to visitors. If you comment on blogs anonymously, you are essentially invisible.
And here is the thing:
We WANT to visit you back!
Visiting back is common courtesy during A to Z. You might not have the time every day to do it, but it is polite to catch up and visit back whenever you get the chance. Leaving sigs in comments also brings new people to your site!
In order to make it easier for people to visit you, you are encouraged to leave a clickable link to your blog at the end of your comment.
You can just copy-paste your blog's URL if you want to.
But if you want to be even more smooth, elegant and helpful, you can create a signature.
Signatures are HTML coded, which means they show up as clickable links. Mine looks like this:
Multicolored Diary - Epics from A to Z
MopDog - 26 Ways to Die in Medieval Hungary
In the HTML code, it looks like this:
multicoloreddiary.blogspot.com ">Multicolored Diary</a> - Epics from A to Z
blogspot.com">MopDog</a> - 26 Ways to Die in Medieval Hungary
You can just copy and paste it, and swap the links and titles for your own!
Make sure you save it somewhere handy (I have it as a Draft in my Gmail box) so you don't have to re-type it every time you go on a visiting binge! You can just Copy and Paste, easy peasy.
Most commenting systems allow HTML, which means your sig will show up nice and clickable. Some might make it show up like the second example (Google+ does that sometimes) but the links are still clickable, and that's what matters.