Where can I buy DeFi?

Excuse me, could you please clarify where exactly one can purchase DeFi tokens or invest in decentralized finance projects? I'm new to this space and have been hearing a lot about the potential benefits of DeFi, but I'm not sure where to start. Are there specific exchanges or platforms that cater specifically to DeFi products, or can I access them through more traditional cryptocurrency exchanges? Additionally, are there any factors I should consider before making an investment in DeFi, such as the security of the platform or the reputation of the project? Thank you for your help.