A product can be removed from one sales channel, or multiple sales channels at the same time. You can do this in a number of ways.
You can click on the channel icons on a product row.
Or, you can click the Actions dropdown (the 3 dots) and select "Manage channels".
Either way, you'll be taken to a modal that allows you to choose what sales channel you want to remove the product from.
Click the "Remove channel" button and your product will immediately be made inactive on that sales channel.
Use the checkboxes on the left-hand side to select multiple products. Then at the bottom of the page, you'll see a bar appear that allows you to take bulk actions. Click the button that says "Remove channels".
You'll see a similar modal to the individual one, except this one allows you to select multiple channels to remove the product from at the same time.
Click the "Save and continue" button and your product(s) will be removed from all of the selected sales channels.