For the butter, "softened" means a little warm (like it would be in the summer if you don't have air conditioning and don't live in the Great White North). If you keep your butter in the fridge, microwave it until it just starts melting a tiny bit. For the sugar, combine the white and brown however you want; I use about half and half and like it. Remember to wash the eggs; cookie batter is awfully yummy.
Combine the butter, sugar, and eggs; beat with an electric mixer. Add the flour, baking soda, and vanilla, and beat again. Add the chocolate chips and stir with a spoon. Put on a cookie sheet. Bake at around 350 degrees Fahrenheit until the cookies just barely begin to turn brown around the bottoms, which will likely be around 10-15 minutes. If you bake longer, you will get crunchier cookies.
You can play all sorts of games with this recipe (add nuts, replace some flour with cocoa for really deep chocolate cookies, put in instant coffee, etc.)