The "i before e" rule is a common guideline in English spelling that suggests the letter "i" should come before "e" in words, except after the letter "c." For example, in the word believe, the "i" comes before the "e." This rule helps with many words, making spelling easier for learners. However, there are exceptions to this rule. Words like weird and caffeine do not follow the "i before e" pattern. Additionally, some words with the "ei" combination, such as receive, follow the rule when preceded by "c." Understanding these nuances can help improve spelling skills.