TTL - Transistor Transistor Logic. TTL devices make use of bipolar transistors.
The main distinguishing features of the basic TTL family is that they demand a power rail which is very close to +5V,
and they use a relatively high amount of current to drive their logic levels
(below 1V for a logical ‘0’ or ‘low’, and above about 3.5V for a logical ‘1’ or ‘high’).
PWM - Pulse Width Modulation. Although a digital signal can only be high or low PWM allows the proportion of time the
signal is high or low to be varied in an analogue fashion.
What laser have you found do you have a link to it's technical specs?
Which connectors are you referring to on the Uno?