Grammar JLPT Level N4 - Lesson 8

In a similar way to みたい, ようだ is used when making observations about something in Japanese. This auxiliary verb is used to express three primary things.
たとえ - Using (A) as an example to highlight the way that (B) looks/is acting.
推定(すいてい) - Using (A) as a reason for an assumption made about (B).
例示(れいじ) - Presenting (A) as an example of what (B) is.
ようだ is usually based on direct information/experience, and shows that the speaker has high confidence in what they are saying. It may also frequently appear in its kanji form, 様(よう)だ.
ようだ can be used with any verb, い-Adjective, な-Adjective, or noun. However, it requires な before it when used with な-Adjectives, or の when used with nouns.

• ここに大(おお)きなビルが出来(でき)るようだ。
  It seems like a big building will be made here.
• あそこのプールは深(ふか)い様(よう)だ。
  It seems like the pool over there is deep.
• 彼(かれ)は明日(あした)のテストに自信(じしん)があると皆(みんな)に言(い)っているが、本当(ほんとう)は不安(ふあん)なようだ。
  He is telling everyone that he is confident about the test tomorrow, but it seems like he is actually worried.
• ヨーダは宇宙人(うちゅうじん)のようだ。
  Yoda appears to be an alien.

Although ようだ and そうだ are often used in similar situations, そうだ shows that the speaker has a lot less confidence in their statement than ようだ. Because of this, ようだ is a much better choice when stating things that are obvious/observable by anyone.