You could use many "normal" appliances, though not at the same time! Not a good idea to use more than one high-wattage appliance (generally anything with a heater and/or motor) at a time.
See this C&CC page which has a pdf link to further advice, including wattages of commonly used items.
It depends on amps supplied to campsite ehu. If its 16amps then you can use high current appliances no probs. If 10amps then just about but one at a time. If it gets hot like toaster, kettle or fan heater then its high current so use these only one at a time and you are ok. TV, fridge or phone charger are only low current drain so you can leave them on. Campsite will advise you on amp rating of its ehu.
At the bottom of this page is a Watts to Amps conversion chart. All your electrical appliances will have their wattage stamped on them (or on a label). You need to work out what amps each item will draw and make sure, if you are using more than one item together, that their total amps does not exceed that supplied by the campsite or your EHU cable.
The majority of EHU cables have 10 amp protection (some may protect up to 16 amps) so I always work to 10 amps. For example, a 2000 watt fan heater will draw 8.69 amps. A 100 watt light bulb will draw 0.43 amps so if you use both together you will be using 9.12 amps. If you keep below 10 amps in total you will be fine.