What is the difference between bauen and erbauen?
I mean, semantically. Or can they be used interchangeably?
No. Erbauen means rather to erect and bauen, to build and I can't think of better examples as those given by @Em1 in the comments.
Rom wurde auch nicht an einem Tag erbaut
Often the prefix er means the prefix "re" in English; however I think that one has to learn each verb separetly (I mean, the verb alone and with prefix), because the meanings of the verbs
er+verb are not always guessable. The link above exhibits the pairs
- trinken and ertrinken, which mean to drink and to drown=drink repetitively to death
- zählen and erzählen, to count and to re-count
- kennen and erkennen, to know and recognize.