A "wallet" is simply a concept. An application which holds and generates addresses to receive and send Bitcoin, as I said, is what most of us call wallets.BTW, is there a limit to how many wallets you can use? Do you use a minimum of 2 wallets or just one to hold all bitcoins, eth, dash, ripple etc?
One wallet can generate an infinite amount of addresses, and if you really want, you can have multiple wallets. Some wallets conflict with themselves when they are installed on top of each other (Not a Bitcoin limitation, it's just that that's how the application was made)
For each altcoin (dash, ripple, litecoin, etc), you will need a different wallet, since these connect to different networks, and may run on modified protocols.
I'd recommend keeping all your Bitcoin in one wallet, until you have a large sum (over a couple of thousand dollars), then moving to either a hardware wallet solution (like a Trezor or Ledger wallet, as in the title post), or using a paper wallet to store the majority of your coins.