Hi,
I can understand tab but have started trying the 12 bar blues and something bothers me.
I'm used to tab like this:
D
e|-------2-----------2-----|
b|-----3---3-------3---3---|
g|---2-------2---2-------2-|
d|-0-----------0-----------|
a|-------------------------|
e|-------------------------|
And know that the numbers tell you which fingers to put where, like above you're playing a D:
But with the 12 bar blues the tab is stilll telling you where to put your fingers, and I can play it okay. But I am confused...

What is the D at the top for, as you're not putting your fingers where you should to make a D... so it confuses me. Or is that string an open D or something?
Any help appreciated, thanks.