The symbols are explained in your basket (where you have your matches). You have to click on the question mark next to the word “messages” to get their definitions.
Symbol in the shape of a conversation bubble : the conversation started with a crushnote.
Symbol in the shape of heart-shaped glasses: he/she liked you because he/she saw that you liked them.
Symbol in the shape of a basket: he/she found you thanks to the “Pollen” feature. Symbol in the shape of a circle with 4 holes: he/she found you thanks to the "Filter by fruit" feature.