What’s the difference between my balance points and my tier points?

The points balance displayed on the home page of the app shows the current balance of points you have earned since joining the program. These are the points you can redeem for discounts and other benefits.  
Redeeming points does not have an impact on your current member tier level. Therefore, your tier level cannot downgrade when you redeem points.  
Your tier points are in fact a counter that calculates all the points you have accumulated during a 12-month period, with its starting date being your tier anniversary date. Those points determine your member tier level (Pro, Elite, Platinum, Master). The tier points are therefore reset to 0 after every 12-month period. 
You can reach a higher tier level (Elite, Platinum or Master) by accumulating respectively 3 500 points, 11 000 points and 45 000 points during a 12-month reference period.