Question: Why do Buddhists make light offerings at Buddhist shrines?
Answer: This is done mainly to remind us to seek the light of wisdom via sincere and diligent Dharma learning and practice, which will banish the darkness of ignorance.
Question: Are there differences between offering butter lamps (in many Tibetan Buddhist practices) and electric (or electronic) lights?
Answer: The difference is that traditional butter lamps are not vegan, as they use clarified yak butter or ghee. (These are not the same as vegetable oil lamps, now readily available worldwide.) Thus, electric lights are kinder. Other advantages include being more convenient, while not having smell, pollution or fire hazard.