All these have the features of a professional program. Some programs, like the ones mentioned above, are so big they come on more than one disk, and may be priced differently than single-disk programs. First you'll need a modem, which lets you connect your computer to the phone line. So, what's the catch, you might ask. Well, a shareware program is meant to be a trial program.
Registration is outlined in the program itself, or the documentation that comes on the disk.
For registering, you will usually get a package of items from the author than can only be gotten by registering. This usually includes a copy of the latest version of the program, sometimes with extra features, and a printed instruction manual. Other items might include free or low cost updates to the program when available, phone support from the author, or other programs the author has written. It really is worth it to register the program. After all, you've gotten the opportunity to inexpensively try the program to make sure it will fill your needs.