The fourth commandment requires believers to keep the Sabbath holy by devoting themselves to worship for the entire day, not just publicly but privately too. This includes forsaking unnecessary thoughts about our activities during the rest of the week.
The fourth commandment requires us to remember the Sabbath by setting apart one day in seven as holy to God. Initially, this pointed to God's rest from creation, but now it points to the rest which is found in the risen Christ.
The second commandment explains how we should worship the one true God. It forbids us from using images or idols as part of our worship, as these only diminish our perception of God's majesty and holiness.
The first commandment requires us to acknowledge that there is only one true God and to worship and glorify Him accordingly, it warns that God is displeased when we give that worship and glory to anything else.