1x means one front chainring; 2x means two. A single-ring system removes the front derailleur and simplifies shifting. With a wide-range cassette it can provide easy climbing gears, although the jumps between gears tend to be larger.
A double-ring setup often offers smaller gear steps, helping riders maintain their preferred pedalling rhythm on tarmac and smooth gravel. It has more components, and some ratios overlap.
Compare the actual specification: divide front chainring teeth by rear sprocket teeth. For example, 40/42 is about 0.95, while 30/36 is 0.83. With equal wheel sizes, the second example gives an easier gear. Before buying, assess the lowest gear with your planned luggage and whether the gaps suit your riding rhythm.