Daniel uses animals such as a lion, bear, leopard, dragon, goat and ram to refer to nations that controlled large parts of the area around the Middle East. The lion (Dan 7:4) symbolised the Babylonians, the bear (Dan 7:5) symbolised the Medo-Persian empire, the leopard (Dan 7:6) symbolised the Greek empire, and so on.
In Revelation, it is more difficult to identify what each dragon or beast stood for, and at least one appears to symbolise sin itself (Revelation 20:2).
Of course, it would have been possible for God to provide a more plain and direct prophecy instead of describe these remarkable animals, but that would have made it much less interesting, and would remove some of the effort required to search out the meaning of Scripture. You could say the same thing about Jesus parables, and he explains why he preferred to speak in parables rather than more plainly:
Then the disciples came and said to him, “Why do you speak to them in parables?” And he answered them, “To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given. For to the one who has, more will be given, and he will have an abundance, but from the one who has not, even what he has will be taken away. This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand. (Matthew 13:10-13)
In other words, he wanted to sift out people who were not willing to delve out the meaning.
Understanding the Bible requires effort, but it is fascinating to try to explore what God has revealed and to discover what the various animals of Daniel and Revelation mean.