Exodus 30:1

And thou shalt make an altar on which to burn incense of perfumes: of sitta wood shalt thou make it.

AND THOU SHALT MAKE AN ALTAR TO BURN INCENSE UPON. Now the altar of incense being one of the articles in the inner part of the Sanctuary, it should have been mentioned with the table and the candelabrum together with which it was placed, as indeed they are mentioned at the actual construction in the section of Vayakheil. But the reason for mentioning it here after the Tabernacle and all its vessels and the sacrifices [for the seven days of consecration], is because of what He said at the completion of them all, and the Tent shall be sanctified by My Glory; and I will dwell among the children of Israel., Verse 45. Therefore He now said that they will yet be obliged to make an altar for the burning of incense — to burn it for the glory of G-d. This was a secret which was transmitted to Moses our Teacher, that the incense checks the plague. For the incense is of the attribute of justice, as it is said, they shall put incense ‘b’apecha’, is of the root aph (anger). which is of the root v’charah api (My wrath shall wax hot). It is for this reason that He said of strange incense, and before all the people I will be glorified, meaning that they will know My glory, for He will not pardon your transgression. For this reason too He said here [of the altar of incense], And thou shalt put it before the veil that is by the ark of the Testimony, before the ark-cover that is over the Testimony, where I will meet with thee. For why is it necessary to speak at length of all these matters, and why did He not say briefly, “and thou shalt put it before the ark of the Testimony in the Tent of Meeting,” as He said in the section of Vayakheil? (further, 40:5). But the extended form of the verse here indicates the purport [of the altar of incense].

FOR BURNING INCENSE. But not for a burnt offering, well-being offerings, grain offerings, or libations.

מזבח מקטר קטורת, he will put only a minimal amount of fire on that altar in order to burn the incense thereon. This altar did not have to be hollow, filled with earth, as was the copper altar which was filled with earth in order that the supply of fire be on the earth, literally. On this altar the fire was kept on the gold overlay. Seeing that there was only a minimal amount of fire kept going thereon this did not damage or burn wood underneath the gold overlay.
The reason that this altar has not been mentioned together with the major altar standing outside the sanctuary, details of which the Torah described in Parshat Terumah, is that this altar was not intended to ensure that the Shechinah made its permanent home among the Jewish people. The purpose of all the other furnishings in the Tabernacle was just that. (compare how G’d defined this purpose in Exodus 25,8-9) Its purpose was also not to attract the glory of the Lord into the Tabernacle, as was the purpose of all the other communal sacrifices burnt-offering, gift offerings, etc. Concerning G’d’s response to those offerings we had read in Exodus 29,43 ונועדתי שמה לבני ישראל, “and there I will meet with the Children of Israel.” Moses himself had confirmed that this was the purpose of the furnishings, etc., in the Tabernacle when he said: (Leviticus 9,6) “and as a result the glory of the Lord will become manifest to you.”
The sole purpose of the golden altar was to honour G’d after He had accepted our service with goodwill mornings and evenings. We used this as a means to welcome His presence by presenting the incense. We find that Chronicles I 16,29 expresses this thought, David saying:הבו לה' כבוד שמו ובאו לפניו, “Ascribe to the Lord the glory of His name!”