SSDs are faster, more reliable, consume less energy and therefore produce less heat. Their only drawback is the price per capacity ratio-- because they're still rather new technology.
Swapping your computer's hdd for an ssd will probably be the biggest performance difference you could notice.
What areas does an SSD give you faster speed in? Almost everything really. Storage drives read and write data: things like opening photos in preview, opening an application, booting the computer up, emptying the trash, recording live video and transferring files are all majorly dependent on storage drives.
SSDs also don't use a spinning platter to operate, so your computer will produce less noise, and will be more resistant to sudden vibration/shaking.