Kailangan ang paliwanag tungkol sa ruta.

In Filipino, the present-tense copula is/are is often omitted.

So Kailangan ang paliwanag tungkol sa ruta is literally something like:

Necessary the explanation about the route

but in natural English we say The explanation about the route is necessary or An explanation about the route is needed.

This is very normal in Filipino. Many simple descriptive sentences work this way.

Here, kailangan is functioning like a predicate adjective or predicate word meaning necessary / needed.

So the sentence structure is basically:

• Kailangan = necessary / needed
• ang paliwanag tungkol sa ruta = the explanation about the route

In other contexts, kailangan can behave more like need in English, especially when followed by ng:

• Kailangan ko ng tulong. = I need help.

So learners often see it used in more than one way.

Ang marks the topic or pivot of the sentence. In many cases, this is the part that feels most like the English subject.

Here, ang paliwanag tungkol sa ruta is the thing being described as necessary.

So the sentence is saying that the explanation about the route is what is necessary.

Important: ang is not exactly the same as English the. Sometimes it matches the, but really its main job is grammatical marking, not just definiteness.

Because predicate-first word order is very common in Filipino.

So instead of starting with the subject-like part, Filipino often starts with the description or predicate:

• Kailangan ang paliwanag tungkol sa ruta.

You can also invert it:

• Ang paliwanag tungkol sa ruta ay kailangan.

That version is grammatical, but it sounds more formal, more literary, or more marked. The predicate-first version is usually the more natural everyday pattern.

It modifies paliwanag.

So the structure is:

• paliwanag = explanation
• tungkol sa ruta = about the route

Together:

• paliwanag tungkol sa ruta = explanation about the route

So the sentence is not saying that the route is necessary. It is saying that the explanation is about the route.

Because tungkol sa is the normal expression for about / regarding / concerning.

So:

• tungkol sa ruta = about the route

Using ng here would be wrong for this meaning. After tungkol, Filipino normally uses sa to introduce the topic being discussed.

Similar expressions include:

• ukol sa
• hinggil sa

but tungkol sa is very common and natural.

Yes, and that is often a very natural alternative.

There is a useful difference in feel:

• Kailangan ang paliwanag tungkol sa ruta.
  = The explanation about the route is necessary / What is needed is the explanation about the route

• Kailangan ng paliwanag tungkol sa ruta.
  = An explanation about the route is needed

The ang version presents the explanation as the topic.
The ng version sounds more like an impersonal statement that such an explanation is needed.

So both are possible, but the nuance is slightly different.

In many contexts, English speakers will naturally translate it as the explanation, because ang often marks something specific or identifiable in context.

But you should be careful not to force a one-to-one match:

• ang is not simply the word the
• Filipino articles work differently from English articles

So in this sentence, ang paliwanag most naturally feels like the explanation or that explanation, but the exact English article depends on context.

Yes. Ruta is a common word in Filipino, borrowed from Spanish, and it is widely used.

It is especially natural for:

• travel routes
• transport routes
• planned paths or itineraries

Other words like daan or landas can mean road, way, or path, but ruta is the straightforward choice for route.