On mac machines, you can click on the blue apple on
the left-top corner and then select "About this Mac".
it will show yoou the basic info, operating system,
CPU and RAM on a new window. if you click "More
Info" button, you will find more details of your mac.

for your harddisk, find a icon for the drive, then
right click, and then select "Get Info" button to
show info about the drive.