The Solid State Drive is much like the traditional Hard Drive. It has the same funcitonality; it stores information when the computer is off, and there is no power. The main difference is that the Solid State Drive (SSD) has no moving parts, unlike the Hard Drive (HDD ), which is mechanical. The Hard Drive is much like the record player, only the disk spins at around 5200 RPM (rotations per minute) and the arm shoots from place to reading and inscribing data. You can think of a SSD as the same thing as RAM but with the power to hold onto the information without electricity.
Today SSD's are becomming more and more popular. Many computers bought today have the option to have a Solid State Drive or a SSD and HDD. One might have a computer with both, the operating system on the SDD for a quick boot up and the HDD for a large movie collection. Graphical engineers, or people running very intense programs often opt to get SSD's as they read and write information more quickly. This means that even the start up time of your computer will be shortened. Solid State Drives also produce a lot less heat then a HDD, which is good if you already have a high end CPU , or graphics card producing a large amount of heat. From a report on PCWorld if users opt to have an SSD put into their Macbook Pro it will be 55% than that of the HDD that normally comes stock in the laptop.
Believe it or not, SSD's do have a drawback. While they have no moving parts they actually do get worn down. Each cell inside the SSD needs to be reset when information is written, erased and wrote over again. This builds up an electrical charge which over time can cause the SSD to require too much power. When it reaches this point the cell is no longer useful and is not used anymore. Slowly the size of the SSD and its speed will slow down. But this is still pretty good compared to a Hard Drive which have much shorter lifes. Since HDD's actually have moving mechanisms there is a much higher of failure, one reason people periodically back up their HDD to an external one.