His main source of calories should be breast milk or formula (as previously said) But you can absolutely start introducing other foods. Most people start with rice cereal (made with formula or breast milk) for 3 days, then other single foods (pureed or cooked until soft and cut into small pieces). You do one food for 3 days before introducing the next so if he doesn't do well with one you know which it was. Good starters are avocado (just mash), peas (steam and puree), squash, sweet potatoes, carrots (look for low nitrate source ones), leafy dark greens, fruit (bananas - just mash, pears, peaches, melon, mango). He is old enough for cooked meats/fish once you have started the veggies and fruit. Just make sure they are well cooked and chopped finely enough he won't choke. No honey until he is 12 months due to the risk of botulism. Salmon is better than tuna because much tuna is high in mercury. Once you have tried these foods as single ingredients, he can start eating whatever you are eating - just puree or chop it finely.