according to Cambridge dictioinary: appreciate - to recognize how good someone or something is and to value him, her, or it: There's no point buying him expensive wines - he doesn't appreciate them. or to understand a situation and realize that it is important: We appreciate the need for immediate action. Thanks - words or actions that show you are grateful or pleased about something: They expressed their thanks to the organizers. He wrote a letter of thanks to the hospital. Let us give thanks to God. I can suggest that they are quiet similar but used for different situations/context there is also already asked same question, so here is reference: https://www.italki.com/question/144308