感到 (gǎndào) means 'to feel' a specific emotion or sensation that arises from a situation, like feeling happy or tired. It is more concrete than 觉得 (juéde), which expresses an opinion or thought ('I think/feel that...'). 感觉 (gǎnjué) is broader (both noun and verb) and can mean a general 'feeling'; 感受 (gǎnshòu) emphasizes experiencing something through direct involvement.