Is Ireland two countries?
Yes! The south part of Ireland—today known as the Republic of Ireland—succeeded from the UK after the War of Independence in 1922. The northeastern tip—aptly referred to as Northern Ireland—decided to remain part of the UK.
How does that affect modern day travelers?
While Northern Ireland uses pounds, the Republic of Ireland uses Euros. The public transportation systems are split, and while road signs in Northern Ireland indicate miles per hour, you’ll see kilometers listed in the Republic of Ireland.
Currently, the border between Northern Ireland and the Republic of Ireland is hardly discernible and it’s not likely that your passport will be checked. But all that might change depending on the outcome of upcoming Brexit discussions.