Hi Adwait,
The get_actual_tcp_speed() is a function who return the actual speed of the TCP anytime you need it. For the function get_target_tcp_speed() it will give you the tcp speed for a specific position. That why you need to enter the pose number as argument. (See attached)
I am new to UR script programming, trying to make a program to move the UR5 robot between two waypoints.