When can babies start on actual SOLID foods?

My family and I went out to dinner and I let my 8 month old suck on a pickle (like you get with burgers on the side at restaurants). I held it and kind of just let her taste it while watching her closely. She loved it and before I knew it she lunged at it and bit off a small piece of the soft part. We all panicked for 5 minutes as I put my finger in her mouth and tried to get the piece out but she had already swallowed it. She didn’t choke (thank god) but it made me wonder when babies can start on small, soft chunks of solid food and what are the best foods to start them on?