der Inhalt
contents
What is inside a container, package, or room.
Der Inhalt des Pakets war leider zerbrochen.
Unfortunately, the contents of the package were broken.

content
Loading your saved state.
contents
What is inside a container, package, or room.
Der Inhalt des Pakets war leider zerbrochen.
Unfortunately, the contents of the package were broken.

The word 'Inhalt' (content) is made up of the preposition 'in' and the noun 'Halt' (hold/support). So it literally describes what is 'held' inside something.
Der Inhalt der Kiste war schwerer als erwartet.
The contents of the box were heavier than expected.
'Der Inhalt' corresponds to the English noun 'content' (what is inside something). But it must not be confused with the English adjective 'content' (satisfied).
Bitte fassen Sie den Inhalt des Textes zusammen.
Please summarize the content of the text.
You can recognize the meaning of 'Inhalt' (content) from the context. In connection with containers (bottle, package), it refers to the physical contents. With media (book, film), it is about the topic or content. With foods (yogurt, juice), it refers to the proportion of a substance.
Der Inhalt der Flasche reichte für zwei Gläser.
The contents of the bottle were enough for two glasses.
When referring to the topic or content, 'Inhalt' (content) is often combined with verbs like 'zusammenfassen' (to summarize), 'verstehen' (to understand), or 'wiedergeben' (to reproduce/relay). Typical nouns are 'Buch' (book), 'Film' (film), 'Gespräch' (conversation), or 'Vortrag' (lecture).
Ich habe den Inhalt seiner Rede nicht ganz verstanden.
I didn't fully understand the content of his speech.
topic / theme
'das Thema' and 'der Inhalt' can both say what a text, conversation, or film is about. 'das Thema' more often names the central subject, for example 'Umweltschutz' (environmental protection) or 'Familie' (family). 'der Inhalt' more often means what is actually said, told, or explained. Learners confuse the words because both answer the question of what something is about. In practice: 'das Thema' is often short and general, while 'der Inhalt' is more specific and includes more details.

Zur Vorbereitung liest sie im Bus den Inhalt des Artikels noch einmal.
To prepare, she reads the content of the article again on the bus.
Das Thema des Vortrags ist gesundes Essen im Alltag.
The topic of the presentation is healthy eating in everyday life.