Is there an easy way to move my photos and videos to a portable drive and delete them from my Mac?

What model and year is your Mac?

How big is your boot drive and how much free space is on it?

What system are you running?

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

If you're strapped for space on your boot drive just copy your Photos library to the external drive and run it from there. Be sure to make sure the library on the external drive works as expected before deleting from your Pictures folder.

If you're going to run your library from an external drive it should be an SSD and formatted as APFS in order for it to be safe and reasonably fast. An HDD should be formatted OS X Extended (journaled).

If the above is not to your needs then gather the photos you want to move to the EHD in an album. Select them all and export them as Unmodified Originals to a folder on the external drive. Make sure the export went OK before deleting the photos from the album.

Where are your photos exactly?

If they are in a folder, you can drag and drop the entire folder to an external drive. No need to do it one by one.

If you are using the Apple Photos App, you can move the entire Photos Library.photolibrary file out an adequately formatted external drive.

click here ➜ Move your Photos library to save space on your Mac - Apple Support

If using a 3rd party app to manage photos, then what you can do and how to do it, would depend on the app you are using.

In addition to Phil0124's excellent advise.

It would be wise to use 2 external drives if you plan on moving your Photos Library.

One external drive to hold the Photos Library and a second external drive to backup the Photos Library.

If you already have an external drive for Time Machine, then by default it should continue to backup your Photos Library.