Te-form of copula (-です) and na-adjective
(Refer to DBJG Te pp.464 467 for more sample sentences.)

This form let adjectives connect to other adjectives or verbs.  

"です" changes into "" + another sentence.

Na-adjective root + "" + another sentence.

Note: You can say “just simply take out “–.”  A comma can be used right after “de."

In the past, we used these choppy sentences: 名前は、一郎です。 年は18才です。 せんこうはアメリカ文学(ぶんがく)です。If we use te-form of desu, these sentences can be connected smoothly as follows:

名前は、一郎年は18才 せんこうはアメリカ文学(ぶんがく)です。
(lit. My name is Ichiro, age is 18 years old, and major is American Literature.)

The same structure and rule applies to na-adjectives as follows.

(lit. This restaurant is pretty, (quiet,) and inexpensive.


Compare the above sentence with what you have learned.
Lit. This restaurant is tasty, (quiet,) and inexpensive restaurant.

Note 1 Te-forms do not indicate any past or non-past form.  You need to see the endings of the sentences to see if it is past or non-past.
10年前、このレストランは、きれい、(しずか、)やすレストランでした。Lit. This restaurant was tasty, (quiet,) and inexpensive restaurant.

Note 2: Do not overuse this structure.  Connecting 2 or 3 sentences is enough; otherwise, it sounds redundant/ unnatural.