Aperture: The size of the opening in the lens when you take a picture - kind of like the size of your iris when you focus your eyes.
It's measured in f-stops, and this is where it gets confusing (for me) - the bigger the hole, the smaller the f stop number. Yep, totally backward and I'm sure it's for a great reason, but the only reason you have to remember that it's backward is...
bigger hole = more light comes in = small f-stop
more light coming in = brighter picture
small f-stop = brighter picture
...don't you love word math? :)
maybe you don't, so I have visual examples too...
Aperture also controls depth of field, which is a fancy way of saying how much of your picture is in focus. In this case the f stop number makes a lot more sense: small f stops mean small areas of focus - large f stops mean large areas of focus. (I don't know if that's really what's "happening," but it's how I remember it.)
Very fun. Very artsy. VERY handy.
So, let me briefly apply this to interior pictures.
1. If you want to take a picture of your entire living room, you need it to all be in focus so you should use larger aperture. When you're focusing on all your little pretty treasures, you can mess around with blurry backgrounds to create intimacy and delicacy.
Little treasures with a smaller f-stop for intimacy
A view of my living room with higher f-stop for clarity
2. If you're taking photos for your latest DIY project, clear how-to pictures are important, but you might want to glam up your after pictures with a little aperture.
Detail of a DIY step with high f-stop for clarity
A fun "after" pic of a DIY with low f-stop for fun :)
(In the spirit of full disclosure, the DIY high f-stop picture is a set up. The project doesn't require needle nose piliers, but I couldn't find my hammer. I wanted an example for this post. Faking karma got me back though - it took about 15min just to take this picture because my cat kept photo bombing it. Divas sheesh....)
Anyway, the best way to learn about aperture is to mess with it. It's a ton of fun and gives pretty instant gratification :)