If you're looking to insure your townhome, the first thing you need to find out is what the master policy covers.
The master policy is the policy owned by your townhome association. Most townhome associations have one, and if yours does, ask for a copy.
When reviewing the master policy, find out what exactly what the townhome association does and doesn't cover.
Most master policies provide coverage only for the exterior of your unit. In addition, coverage for common areas such as parks, pools, club houses, etc...
As the owner of a townhome, in most cases, you own only the inside of the unit and share ownership in all common areas. Thus, you're insuring the interior of the dwelling (including your contents), the structure, and the property it's built on.
If this is the case, you're looking for an HO-6 policy, which is the fancy insurance term for townhome insurance you may come across.