A nominal sentence starts with a noun, like “The sun is shining” (الشمسُ مشرقةٌ). A verbal sentence starts with a verb, like “The sun rose” (أشرقتِ الشمسُ) or “The boy plays” (يلعبُ الولدُ).

A nominal sentence has a “subject” (مبتدأ) and a “predicate” (خبر): «الشمسُ» is the subject and «مشرقةٌ» is the predicate that tells us about it. A verbal sentence has a “verb” (فعل) and a “doer” (فاعل): «أشرقتِ» is the verb and «الشمسُ» is the doer.

Notice the same idea can be said two ways: «الطفلُ يكتبُ» (nominal — “The child writes”) and «يكتبُ الطفلُ» (verbal — “Writes the child”) — both are correct, only the word order differs.