IB gives you the option to choose a subject at either Higher Level (HL) or Standard HL (SL). As the name suggests, HL has more depth and knowledge and SL is merely an overview of the subject. 

Math SL has mainly 6 topics (140 Hours) namely:

-Algebra (9 Hours)

-Functions and equations (24 Hours)

-Circular functions and trigonometry (16 Hours)

-Vectors (16 Hours)

-Statistics and probability (35 Hours)  

-Calculus (40 Hours)

Math HL has 7 Topics (6+1 Additional Topic) (182 hours) 

-Algebra (30 Hours)

-Functions and equations (22 Hours)

-Circular functions and trigonometry (22 Hours)

-Vectors (24 Hours)

-Statistics and probability (36 Hours)  

-Calculus (48 Hours)

Additional Topic Options:

-Statistics and probability (48 Hours)  

-Sets, relations, and groups (48 Hours)   

-Calculus (48 Hours) 

-Discrete mathematics (48 Hours)

Math HL is clearly more difficult than SL. It not only has the same topics as SL but they are more in depth. Also, an additional 48 hour topic is an icing on the cake.