An ADSL router is to be used with ADSL connections only through your local phone company. it is usually a modem/router combination unit...meaning that the ADSL modem is part of the wireless router. You can connect/network with this type of router just as with any other broadband/cable router....only that you may find that it has limited connections set up by the phone company....They may only allow 5 computers to connect to the router or maybe 10. For sure the wireless range is lowered to only allow connections from close proximity while regular routers will broadcast about 300 feet or so.
This is regulated by the phone company and if you want more range ...you will have to pay for it.
I tell my customers that have to rely on an ADSL connection to request a modem only and not a combination ADSL modem/router combination....Once the ADSL is set up then I have them install a regular either wired or wireless router to the ADSL modem....This allows for better connectivity and less control over your network by the phone company.