Can I change Fill Factor option for our database server?

I have a production database for ERP which has clustered and non clustered indexes. Some other tables have index type as heap and i don't understand what does heap means. Every month i have a job run this command sp_msforeachtable "dbcc dbreindex('?')" to rebuild all indexes in our database after that i checked the fragmentation and i found it to be still 98%. I searched on web to discover that our Fill factor option for our server is 0, so can i change it to suitable percentage and what factors I need to consider?