1. Explain it simply
确实 means 'indeed / really'. It stresses that something is genuinely true, based on what you know or have seen.
Word order: Subject + 确实 + verb / adjective. It comes after the subject and before the predicate.
Unlike the exclamation 真, 确实 sounds like calm, considered agreement - 'yes, it really is so'.
Do not put 确实 at the end of the sentence.
2. Show examples
这家饭馆的菜确实比别的地方便宜。
Zhè jiā fànguǎn de cài quèshí bǐ biéde dìfang piányi.
This restaurant's dishes really are cheaper than other places.
确实 before the 比 comparison
今天确实很热。
Jīntiān quèshí hěn rè.
Today really is hot.
确实 + adjective 热
他确实会说汉语。
Tā quèshí huì shuō Hànyǔ.
He really can speak Chinese.
确实 + verb phrase 会说
3. Share a tip
确实 goes before the verb or adjective, never at the very end - say 他确实来了, not 他来了确实。