What is the best type of exercise for someone with lower back pain?

It can vary depending on what’s causing your low back pain. In general for many it’s due to week abs & tight lower backs & poor posture.

Work on strengthen both your abs/back (your core muscles) while also stretching your back & probably glute & hamstrings are tight too.

Start standing straighter & use your muscles (not joints) to hold your body upright. We tend to allow our joints/bones to do the work & not our muscles which is what they are ment for.

Pilates & yoga are great places to start to learn to work from your core.