blockchain has new design recently. I'm a little bit confused with that. so I wanted to make a new address, but when I clicked "receive", there is this caption "A new address has been created for you to share with others in order to receive bitcoins."

so I have a new address, but how about my old address? still it can receive fund or not? and can I receive funds from that 2 addresses? or only one of them? should I always set it before sending money or receiving money?

thanks for the answers.