A more thorough explanation:

The position of the United States refers to the legal stance taken by the federal government in a lawsuit. This is especially important in cases that involve the Equal Access to Justice Act (EAJA).

Under the EAJA, the government may be held liable for the opposing party's attorney's fees if their position is deemed unreasonable in light of legal precedent. In other words, if the government's position goes against established legal principles, they may have to pay the other side's legal fees.

For example, if the government is sued for violating a citizen's constitutional rights and they argue that the Constitution does not apply in that situation, their position may be deemed unreasonable and they may be required to pay the citizen's legal fees.

Another example could be a case where the government is sued for environmental damage caused by a federal agency. If the government argues that they are not responsible for the damage because it was caused by a third party, their position may be deemed unreasonable if they had the power to prevent the damage and failed to do so.