Shareware is copyrighted, but you can download it freely and trial it to make sure it's suitable to your needs. After satisfying yourself that the software is suitable, you must register and pay for it. Trial periods for shareware can vary from a week to 90 days after which most will generally cease to work. Adware is a program that carries advertising. They are typically programs that connect to the Internet so that the ads can be rotated.
Adware programs are free to use, however, many support the option to purchase the program.
Trialware is very similar to shareware though. As with shareware they will cease to work after the trial time limit.