What is bitless riding? 

I like to see this term a little wider than the literal word. I don't mean only without a bit, but also with the least pressure possible. Bitless riding is not just throwing on a halter and pulling hard on the nose. Bitless riding is riding on feel, riding with your body and your seat. You get to know each others subtile signals, what helps you react on each other on a deeper and softer level. You learn to ride in connection. And step by step you trust more on each others bodies, in stead of on the right gear.

Is it dangerous to ride without a bit or without a bridle? 

Horseriding is a risk itself. You work with living animals and you can never 100% predict the situation. Byut by working from a point of trust, without force or pain, you make the risk on a heavy reaction smaller. Horses will be less temped to buck, rear or run away, when you explain them what to expect and you consequently help them find softness again.  So from my point of view, the risk is not connected to the bridle. And in that sense, it can even be safer to ride without, because you can not force the horse over it's own boundaries. 

Can every horse be ridden bitless? 

​In principle, any horse that is ridden with a bit can also be ridden bitless. Of course, this is a learning process. You cannot simply swap in a new bridle and expect your horse to understand what you want. That’s why it’s important to include a transition period.
You can start from scratch, gradually teaching your horse step by step what you mean with the new tack, or you can initially combine the new and old tack to show your horse which cue requires which response. For some horses, due to distrust or past trauma, this can be a longer process.
We can explore together which tack suits your horse best.