FreePBX is a PABX, which ultimately will require you to connect to a provider (most often this is via SIP) that allows you connectivity to the PSTN. There are many to choose from: Bandwidth, Intelliquent, Skyetel, Vitelity, Flowroute, etc.
PBXAct is Sangoma’s paid FreePBX option, which they also offer SIP trunking services with.
FreePBX doesn’t require you to use VoIP; it can also use analogue or ISDN.
Do you mean make and receive calls from the PSTN? Someone has to be paid to provide access to the PSTN. It can however make calls to local extensions and over private networks without that.
(Technically, it can receive calls from suitably configure VoIP systems without using the PSTN, but, for security reasons, people normally block that. Asterisk can make direct VoIP calls, but I don’t believe FreePBX really supports that, and, in the real world, they would be blocked by the recipient’s security measures.)
So, although in principle it can create a functioning system that can make and receive calls, that isn’t useful in the real world, if you want to go outside your own organisation, and you can’t use the PSTN without someone paying.