In the context of U.S.:

You are talking about what is the difference between a Bachelors of Arts in Architecture degree (B.A. in Architecture)  vs. a Bachelor of Architecture (B.Arch) degree.

In general, the B.A. in Architecture is a 4-year degree (if you follow the standard curriculum course load). They are generally deemed PRE-PROFESSIONAL degrees of architecture because the Bachelor's degree itself is NOT accredited by NAAB (National Architecture Accreditation Board). There is also a Bachelors of Science degree in Architecture (B.S. in Architecture). They are also pre-professional degrees in architecture like the B.A. in Architecture and also NOT NAAB accredited. The difference is mainly in the general education requirements. From licensing stand point, they are considered equivalent of about the same weight of recognition. 

B.Arch is a 5 yr PROFESSIONAL degree of Architecture at the Bachelor's level vs. Masters level. They are NAAB accredited.... usually UNLESS the program is misrepresenting or misleading.

To add to your understanding, there is three Masters level degrees....

1 year POST-Professional degree. This is a graduate level degree of architecture recognized by NAAB for those who ALREADY have an NAAB accredited bachelor's degree.

Then there is a 2 Year PROFESSIONAL degree in Architecture for students who have a B.A. or B.S. in Architecture. Resulting in an M.Arch degree (Masters of Architecture). This degree would be NAAB accredited if institution is properly representing the degree. Look for NAAB accredited.

Then you have a 3+ year Professional Masters of Architecture degree for those who have their undergraduate level (bachelor's degree) in some other subject than Architecture such as engineering, geography, computer science, etc.  This degree would be NAAB accredited if the institution is properly representing the degree. Look for NAAB accreditation. 

Any PROFESSIONAL degree in Architecture in the U.S. look for NAAB accreditation.