Mini solar chargers are pocket-sized solar panels of wattage from 0.3 watts to 6 watts with internal batteries that are suitable for charging mobile phones and personal devices.
Larger portable solar panels of 20 to 160 watts can charge up an external battery to provide power for portable appliances when traveling or camping. 
A larger solar panel will generate a higher wattage, and charge up a battery faster than a smaller and lower wattage panel would. 
The battery size indicates how much power it can store before you need to recharge it, so a small solar charger with an internal battery of 3000mAh will hold 3 times the charge of a 1000mAh battery.
Chargers are designed to supply a certain voltage, so you would usually need a charger that can supply 9 volts to charge up your camera, but only need 4 or 5 volts to charge your mobile phone. Some chargers are capable of providing a range of voltages in order to be more versatile.