A RCT is:

1. Randomized (entry or not by the flip of a fair coin) and

2. Controlled.

Your other type of study is not randomized nor is it controlled necessarily.

Randomization.

RCTs are one type of comparative studies (studies with controls).

Non-RCT comparative studies, such as case-control, cohort, and quasi-experimental, although they have controls, lack randomization.

RCT

for trials that contain control groups, in which groups receiving the experimental treatment are compared with control groups receiving no treatment that is a placebo, clients have equal chances of falling under either groups

Comparative

study in which a participant is randomly assigned to one of two or more different treatment groups for purposes of comparing the effects of the treatments

RCT Study and comparative study almost are the same because RCT has two groups experimental and control groups, the same in the comparative study there are two groups which compared to each other though maybe without the experimental group.