I am gonna buy a laptop, what does the number after T signify (like in T7200)?

Answer 1

this is a typification by Intel after testing the CPU chips. it means the chips will be categorized depending on what tests they pass.
in your specific example for the Core 2 Duo notebook chips (Merom core) there exist 6 different denotations: T7600, T7400, T7200, T5600, T5500 and T5200.
the cipher 7 means the CPU has 4MB L2 cache, the 3 following ciphers designate the clock speed but encrypted, the higher the faster.
600: 2.33GHz, 400: 2.16GHz, 200: 2.00GHz

the cipher 5 means the CPU has 2MB L2 cache, the next 3 ciphers designate also the clock speed, but it is lower than on the T7x00 series.
600: 1.83GHz, 500: 1.66GHz, 200: 1.60GHz

the T5200 is anyway a special case, because it's the only one running with a FSB speed of 533MHz whilst all others run with a FSB speed of 667MHz.

Answer 2

Its the model number of the processor. It doesn't really mean anything tangible, like a speed or anything, its just a model number.

Answer 3

here's a link on ebay where you can read reviews of them by ebay members