Difference between select lines and control lines in Digital circuits?
A select line selects something, like a specific chip. A control line is a line that controls something. A select line is a form of control line, along with such things as read, write, etc. 

Common names for control lines include:


/CS - Chip Select (a select line)
/SS - Slave Select (a select line used in SPI)
/RD - Read
/WR - Write
RD/WR - Read / Write 
/OE - Output Enable
/EN - Enable


The list goes on.

Broadly speaking, in a traditional parallel CPU bus, the control lines are all the digital signals that come from the CPU (or go to it) that aren't the address and data, and select lines are decoded from the address bus. In other systems though that is not always the case.