What is the difference between 1tb hard drive and hybrid 500gb +8gb sshd?

The hybrid has an 8GB solid state drive on top of a regular 500 GB hard drive. It is faster than the 1 TB drive as the 8GB SSD will buffer data and is quicker than the mechanical drive. If you don't expect to have more than 500 GB data then get the Hybrid. You should have your data backed up to external drives anyway for safety.

Pretty much as Marduk said. The SSD acts as a cache of the most commonly used files on the hard drive portion, providing faster launching of the system and applications. If you are going to need more than 500 gigs storage then get the 1tb, otherwise get the hybrid. Also, as Marduk said, always back up your important data. You should ALWAYS have your important files copied to a different physical drive than you C drive, preferably on an external HDD, a CD/DVD, a flash drive, another computer (using networking) or a NAS device - a standalone HDD available to those on your network. You could try using cloud storage but the upload speed of most services is such that copying large numbers of files up to the cloud will take a long time.

You should always have an SSD of at least 120GB of capacity. With 8GB, you have the SSD as a cache drive.