Exodus 13:21

And the glory of the Shekinah of the Lord went before them by day in the column of the Cloud to lead them in the way, and at night the column of the Cloud removed behind them to darken on their pursuers behind them; but to be a column of fire to enlighten them before, that they might go forward by day and by night.

In a pillar of cloud. It was shaped not like a cloud but like a pillar extending earthward from heaven. A pillar is called an amud in Hebrew because it is ma’amed—i.e. “holds up”—the house. So that they could travel by day and by night. Because of the enormity of the camp they were only able to travel short distances at a time. Therefore they traveled a brief way in the daytime and then another brief way at night. The two pillars remained with them until the reached the sea.

AND THE ETERNAL WENT BEFORE THEM. The Sages have already said, “Wherever the phrase And the Eternal is mentioned, it means He and His Celestial Court.” The Holy One, blessed be He, went before them by day, and His Celestial Court by night. If so, the explanation of the verse is that G-d abode in the midst of the cloud, and He went before them by day in a pillar of cloud. By night, His Celestial Court abode in a pillar of fire to give them light. This is similar in meaning to that which the verse says: Inasmuch as Thou Eternal art seen face to face, and Thy cloud standeth over them, and Thou goest before them, in a pillar of cloud by day, and in a pillar of fire by night.
I have seen in Eileh Shemoth Rabbah: “For ye shall not go out in haste, neither shall ye go by flight; for the Eternal will go before you. In the past, I and My Celestial Court went before you, as it is said, And the Eternal went before them by day, but in the World to Come, I Myself will go before you, as it is said, For the Eternal will go before you, and the G-d of Israel will be your rearward.” The secret of this Midrash is as I have mentioned, i.e., that at the first redemption, the Holy One, blessed be He, was with them by day and His Celestial Court by night, but in the World to Come, the attribute of His Celestial Court will be elevated in mercy and the Eternal — the Tetragrammaton — will go before them, for the G-d of Israel will then assemble His people, and the night will shine as the day, the darkness even as the light, as everything will then be united in the attribute of mercy.
Rabbi Abraham ibn Ezra commented that Scripture here speaks according to the language of men, since it was the power of G-d and His messenger that went with Israel, [thus, and the Eternal went before them would mean “and the angel of the Eternal went before them”], similar in meaning to the verse, He caused His glorious arm to go at the right hand of Moses. Now it is true that the verse here is similar in meaning to the verse, He caused His glorious arm to go at the right hand of Moses, but it is not as Rabbi Abraham ibn Ezra understood it.. It was this verse apparently that forced Ibn Ezra to arrive at his interpretation here. See Ramban, ibid., for a fuller discussion. And it is further written, So didst Thou lead Thy people to make Thyself a glorious Name, [thus indicating that it was the Holy One, blessed be He, Himself that went before the people, and not, as Ibn Ezra explained, that the reference here is to an angel].

וה' הולך, the angel accompanying the Israelites on their journey positioned himself at the head of the marching columns in the guise of a pillar of cloud by day and a fiery column of flame at night.

יומם ולילה, the reason that they traveled both by day and night was to make Pharaoh rethink his decision and to see in them people who were in flight.

וה' הולך לפניהם, from the time the Israelites had reached Sukkot, at the border of Egypt, just beyond, G’d’s presence had manifested itself the moment they entered the desert.