ATMEL

Following is the basic information that one can extract from a data sheet of a component :

• Type of Architecture
• Memory size
• Peripheral size (Number of pins)
• Special features
• I/O and packages
• Operating voltage
• Speed grade
• Industrial Temperature Range
• Power consumption

ATtiny series

Attiny series consists of the smallest 8-bit micro-controllers. It is usually used for simpler processes and programs. Its features includes Advanced RISC Architecture.

I also checked another diagram which explained the pins briefly.

My notes to understand this diagram :

GND means ground which is 0 volt

Power or VCC indicates voltage.

Current will pass when there is a voltage difference across a node

MISO is master in slave out

MOSI is master out slave in

Digital pins give only 2 outcomes : "on" and "off"

Analog related pin can give variation in voltage and not restricted to "on" and "off"

SCK is serial clock.