If your question is about trouble connecting your device via Wifi, Bluetooth, or USB, or to the mobile network, this is the correct tag.
Connection issues can cover a range of problems:
- the device is not recognized when connecting it to the computer
- it won't connect to your router
- it connects, but the network remains unusable (e.g. the status says connected, but you still cannot access the net)
- similar stuff with two devices and Bluetooth
These are just examples. If your problem is comparable, you should use this tag for your question. Other valid issues may include...
- not being able to use 3G/4G in an area where it should be available
- getting a connection, but always losing it without apparent reason
Apps claiming "no Internet connection", though the device (and other apps) say otherwise might also fit in this category.
See also: data-connection