Picasa is the name of a software which helps the user find, share and edit pictures on your computer. When you open this application it finds all pictures present on your computer.
Then this software manage the pictures in the albums naming the folder and placing the pictures as you will recognize. Sometime you when you your self want to add something in the folder just drag it and put it in the desired folder. You can also create new folders as you desire. By using this software your picture will always be in organized manners.
Picasa have also a feature of one click where it can fix with only clicking once. It makes the snaps ready for you to share via emails etc. Even you can post these pictures on your own blog.
New version of the software have a requirement of having an account on google. This version also adds web albums.