Maarja is the Estonian form of Mary. The double-A reflects the Estonian long vowel — Estonia is one of the few European languages that preserves these long vowel sounds.
Maarja is widely used in Estonia.
Maarja does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Maarja reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.