Start watching from about 2:00
The Hospital Escape scene in Terminator 2 used a revolutionary mix of practical effects and early CGI.
Practical effects (Stan Winston Studio) created most of the physical T-1000 interactions, such as:
Bullet hits and splitting head from shotgun blasts (using detailed puppets and animatronics).
Solid form interactions (Robert Patrick performing stunts).
CGI (Industrial Light & Magic) was used for the unique liquid metal transformations, including:
Seamless morphing and shapeshifting (e.g., transforming from the floor or through bars).
The shimmering, reflective surface of the liquid metal.