The coin (or UTXO) model is a Bitcoin-style transaction model which is also used in Chia. Your wallet keeps track of a set of coins, where each coin can be any amount of XCH. When spending a coin (making a transaction), you have to spend the entire amount, and split that coin into multiple outputs, called coin additions. One addition is to the recipient of the transaction, and the other one is to you, as change. The change usually goes to a new address, so you will not see it in your normal address on Chia explorer, but your wallet will keep track of it and include it in the balance. Each block in Chia is a list of removals (coins spent) and additions (coins created). There are no transactions in the blockchain, which is why you cannot lookup transactions in the block explorers.
