In this chapter, the LORD details the construction of the things outside the tabernacle: the bronze altar and the courtyard screen.
First, note the change of materials in this chapter. While in chapter 25 and briefly in 26 the furnishings were made of gold (except for the bases of the tabernacle, which needed to be weight-bearing), in this chapter all of the furnishings and ornamentation are made of bronze. Partly I think this is because they are external, subject to the elements, and require more durability: I previously noted that pure gold is very fragile, while bronze is a very durable metal alloy that can sustain a lot of abuse. I also think it is because gold is more valuable than bronze, so all of the things closer to the holy of holies are gold, while radiating out from that the courtyard is filled with bronze. Or conversely, we can imagine the effect on Hebrews who go in to the tabernacle and passes first into a courtyard of bronze, past the outer screen and into the holy place where everything is made out of gold, except for the curtains, which are woven fabric of many colors with cherubim everywhere. Then, passing beyond the veil of separation, he enters into the holy of holies where resides the ark of the covenant and the LORD's abiding presence. The effect is to heighten the appearance of majesty and grandeur to the visitor.
The construction of the altar is more elegant than the altars of earth or stone that was recommended before. Now we're seeing an altar of wood covered in bronze, with this bronze network (whatever that means) and some bronze carrying poles. Of course everything has carrying poles because the Israelites are going to carry these things through the desert to the promised land. The "horns" of the altar are small ornaments that don't have any explicit purpose, yet symbolically are used to represent the essence of the altar, in that the Israelites are frequently command to put the blood of sacrifices on the horns. Verse 3 makes it clear that something will be burned on the altar, requiring shovels and pails for the removal of ashes. Later we will see what they are burning. The wood obviously wouldn't handle fire well, so the entire surface of the altar is covered with bronze.
Next, we are told there is to be an outer courtyard which surrounds the tabernacle. This courtyard is notably larger than the tabernacle (which, in the last chapter, we noted was around 22 feet long and 7-8 feet wide). The courtyard, in turn, is a rectangle of dimensions 150 by 75 feet, with the entrance on one of the narrow sides (although I don't believe the text tells us which one). This is another physical barrier to enter the holy place. Although it is open above, towards the sky, it is not open for people to freely enter. I don't think there's anything notable about the structure or design of the courtyard, other than its construction with bronze which I reference above.
Lastly, we are told that the lampstand whose construction was detailed earlier is to be burning continually, which possibly means every day, but more likely means 24/7/365, all of the time, although it would possibly have to be put out while moving from one place to another. I'm not sure about that, maybe later text will make it clear. This is a "perpetual statute", but perhaps most surprisingly is that Aaron and his sons are commanded to do this. We have known that Aaron was Moses's right-hand man for a long time and we also knew that he was counted amongst the "elders of the people" along with his sons Nadab and Abihu, but now Aaron appears to be getting his own particular assignment. In the next chapter we will see that this is a very extensive assignment, but here it is to maintain the perpetually burning flame in the tabernacle.
On a minor note, in verse 21, the author calls the tabernacle the tent of meeting. This is the same structure that we are reading about, but a name that emphasizes the LORD "meeting" with the Israelites there, while tabernacle (i.e. residence) emphasizes that the LORD lives there and it is his home.