Processor. When I bought my laptop is came telling me it had a "Mobile AMD Sempron processor 3400+

Question

When I bought my laptop is came telling me it had a "Mobile AMD Sempron processor 3400+ (1.8 Ghz, 256KB L2 cache)".
When I right click on My Computer and go to Properties it tells me its has a "Mobile AMD Sempron processor 3400+ 792MHz, 448 MB of RAM".

Are these two different or am I reading something wrong???
My laptop always seems to run slower than I thought it would, but I don't know heaps about computers.

Thanks in advance!