Radar imagery is not intuitive to interpret and different electromagnetic frequencies serve different applications
Radar imagery is great for seeing through cloud or darkness, and for revealing information that is not detected by traditional visible or optical sensors. C band and X band refer to different operating frequencies (and wavelengths) of the radars. The X band wavelength is about 3 cm, while the C band wavelength is about 5 cm. This means that the two instruments respond to different types of roughness on the ground. X band is sensitive to finer scale roughness while C band is sensitive to coarser scale roughness. C band is often chosen for soil moisture mapping, for example, because the instrument is less sensitive than X band to finer scale surface roughness which can act as "noise" to the soil moisture information. However, C and X band radar also have slightly different dielectric properties which mean that they react to differences in the electrical-magnetic properties of the materials that they image. C band will penetrate through dry snow more easily than X band for example. It is a complicated topic, but if you have a particular application in mind please get in touch and we will advise you and/or take a look at some background information on radar imaging here.
Different "false colour" combinations of data from Sentinel-1 imagery shown next to Sentinel-2 imagery (right panel) illustrating the cloud-free capabilities and the different types of information from @valpesendorfer.