How can I tell which of these video devices is a webcam?

$ ls -ltrh /dev/video*
crw-rw----+ 1 root video 81, 1 Mai  4 00:17 /dev/video1
crw-rw----+ 1 root video 81, 0 Mai  4 00:17 /dev/video0

This is a laptop so I guess one is the built in camera, and one is the screen. But how can I check which? Is there a way to get more information about one of them?

You can do this with v4l2-ctl in a terminal:

1. Open Terminal (if it’s not already open)
2. Install the utility (if it’s not already installed)

   sudo apt update 
   sudo apt install v4l2-ctl
   

3. Run the utility:

   v4l2-ctl --list-devices
   

   You will see output like this:

   Integrated Camera (usb-0000:00:3b.0-1.2):
       /dev/video0
   

One of the video devices you see in /dev/video* is a virtual device.

There is a package called usbutils which can be an invaluable tool:

sudo apt install usbutils

Then you can query any USB device and get a lot of information:

$ sudo lsusb -v | grep -i webcam -a14

Bus 001 Device 009: ID 1bcf:2b8c Sunplus Innovation Technology Inc. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          239 Miscellaneous Device
  bDeviceSubClass         2 ?
  bDeviceProtocol         1 Interface Association
  bMaxPacketSize0        64
  idVendor           0x1bcf Sunplus Innovation Technology Inc.
  idProduct          0x2b8c 
  bcdDevice           47.14
  iManufacturer           1 SunplusIT Inc
  iProduct                2 Integrated_Webcam_HD
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          767
    bNumInterfaces          2
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              500mA
    Interface Association:
      bLength                 8
      bDescriptorType        11
      bFirstInterface         0
      bInterfaceCount         2
      bFunctionClass         14 Video
      bFunctionSubClass       3 Video Interface Collection
      bFunctionProtocol       0 
      iFunction               4 Integrated Webcam
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass        14 Video
      bInterfaceSubClass      1 Video Control
      bInterfaceProtocol      0 
      iInterface              4 Integrated Webcam
      VideoControl Interface Descriptor:
        bLength                13
        bDescriptorType        36
        bDescriptorSubtype      1 (HEADER)
        bcdUVC               1.00
        wTotalLength          109
        dwClockFrequency       48.000000MHz
        bInCollection           1
        baInterfaceNr( 0)       1
      VideoControl Interface Descriptor:
        bLength                18
        bDescriptorType        36
        bDescriptorSubtype      2 (INPUT_TERMINAL)
        bTerminalID             1