Why do I have more photos on my photo app on my iPhone and iPad than on my photos app on my Macbook?

If you don't see your Camera Roll as a separate album on your iPad and iPhone, you have iCloud Photo Library enabled in the Settings.

But is it also enabled on your Mac? What are the Preferences in Photos on your Mac? Is iCloud Photo Library there enabled as well? Has the sync finished? Are you still seeing a progress bar in this panel, or is it showing "Updated just now"?

To check, if all photos on your Mac can upload to iCloud, you may want to create a smart album with the single rule "Photo is unable to upload to iCloud Photo Library".

File > New Smart Album:

Why do I have more photos on my photo app on my iPhone and iPad than on my photos app on my Macbook?

Which iCloud service are you using with the Photos.app on your Mac and your mobile devices? Are you using iCloud Photo Library, or are you using My Photo Stream?

• If you are using iCloud Photo Library on all your devices, all (compatible) photos will upload to iCloud and from there download to all devices. The Photos libraries on all devices should contain the same photos, once the upload finishes. Your Mac may contain photos that cannot upload to iCloud Photo Library and thus could be showing more photos.
• If you are not using iCloud Photo Library, all your Photos Library could be showing completely different sets of photos, depending on how you transferred the photos there. My Photo Stream, if enabled, will transfer new photos from your devices to the other devices, but it will not ensure that the libraries are in sync.

So what are you using, and how did you transfer the photos to the devices?

Try going to iCloud.com to see if the items are there and whether they are from the device or the computer. That should show whether the device or the computer isn't syncing. If the computer, try going to System Preferences/iCloud and stop syncing. Wait a couple of minutes, then recheck syncing. If the device, go to Settings/iCloud and do the above. You can also try signing out of iCloud and then sign in again.