the short answer
A Romanian deadlift is a hip-hinge exercise: from standing, push your hips back with nearly straight knees to lower a barbell down the front of your legs, then drive your hips forward to stand up. It targets the hamstrings and glutes. The key cue is to hinge at the hips, not bend at the waist.
This article is general training education for coaches and clients, not medical or rehab advice - form is individual and depends on your build, mobility, and history, so a qualified coach giving a live form check is the gold standard for learning the lift safely.