Bittrex is trusted and old cryptocurrency exchange with good trading volume. Bittrex exchange user interface is bit harder for new traders of bittrex but for pro traders its very useful. Deposit fiat money, then buying specific cryptocurrencies for out interest (mostly in the USD market), after few tradings - we convert it again to USD and withdraw this fiat money and transfer it to our customers.
Bittrex exchange with very serious people in charge, they add many coins but after an exhaustive control they avoid adding coins without community support or without active developers.
What stands out most of Bittrex is the large number of listed currencies that have in its platform (more than 100) also counting with a large volume of purchase and sale for each currency. It also provides pairs for BTC, USDT, XMR and other important currencies such as USDC.
As far as security is concerned it provides 2FA verification to be able to enter the account and to make withdrawals of coins use confirmation by email together to whitelist.