What are the different types of promises?

Promises can be categorized into several types based on their nature and usage. The most common types include formal promises, which are legally binding agreements, and informal promises, which may not carry legal weight but are significant in personal relationships. Additionally, there are conditional promises, which depend on specific conditions being met, and unconditional promises, which are commitments made without any conditions. Lastly, express promises are explicitly stated, while implied promises are inferred from actions or circumstances.