I think your bonsai is a Chinese elm, though others should check me on that.
If so, it is a subtropical tree which is sometimes treated like a temperate decidous tree and given a period of cold dormancy in which it drops its leaves and rests and is sometimes treated like a tropical evergreen and kept indoors and growing through the winter.
See https://www.helpfulgardener.com/forum/vi ... 82#p345882
also if you use the search box at top left above the Helpful Gardener logo, you will find lots here about Chinese elms. In the non - Forum part of this website are a bunch of articles on bonsai care, watering, soil, etc. see https://www.helpfulgardener.com/bonsai/
Your white blob is either something fungal like a slime mold or some insect product like spittle bug foam, I'm not sure. Either way, you do not want it there. You should inspect your tree and any other house plant you have carefully for any signs of insects, checking the undersides of leaves and just under the soil surface.
Welcome to the Forum! glad you found us. It always helps to let us know where you are located. There are very few gardening questions, even indoor gardening, that can be answered without regard to season, climate, geography, etc.