200/50 R18 doesn't belong to the most popular dimensions for winter tyres - there are 2 tyre models available, which can be compared to
155/60 R15,
170/60 R17,
160/60 R14. Let's break down the sizing - 50 is height of the tyre, which is calculated as 50% of the tyre width (200mm), which means the sidewall height has 100 mm. The wheel diameter is R18, which means it fits to a 18 inch/457.2mm diameter wheel. The total circumference of the tyre is 2064.65 mm, which is very similar to 205/55 R17
(2064.97 mm), 225/50 R17
(2063.4 mm), 285/35 R18
(2063.08 mm), 160/70 R17
(2060.26 mm), 295/25 R20
(2059.31 mm), 245/30 R20
(2057.74 mm), 295/30 R19
(2072.19 mm).
