Freebies are a big part of getting started in second life. Second Life currency is the Linden Dollar. More or less the only ways to get Linden Dollars are to be given them, buy them, or earn them. Unlike many MMPORGs, the game does not create money which can be gained by doing things or killing monsters. Instead the Linden Dollar is convertible to the US Dollar through things like the Lindex.
This means that when starting out, before buying things with your Linden, if you have any, you should look for freebies which are available in world. This will tell you what is worth paying for, and what is not. Very often people will try and sell you freebies in sandboxes and other public areas.
Freebies range from very useful, to being means of getting you to join a particular activity, like a Combat System, or not very useful at all. Freebies are found in collections, junkyards and in individual freebies that are given away as promotionals. Related to freebies are coupons.
The best way to go freebie hunting when starting out is to be organized and go to the best collections, such as Free Dove and then get your avatar organized. Then hunting for freebies that help with activities that you are interested in, like vehicles.