It lies on the A4076 road approximately midway between Haverfordwest and the port of Milford Haven and is served by Johnston railway station. Until the end of the 19th century, anthracite was mined here. The village is now a dormitory for Haverfordwest and Milford Haven. The parish church has the typical tall, slim castellated tower of churches in English-speaking Little England beyond Wales.
In 2011 11.4% of inhabitants could speak Welsh, down from 13.81% in 2001, but 18.5% had at least some Welsh language ability. This is lower than the overall percentage for Pembokeshire and Wales, which are 19.2 and 19.0 respectively.
Johnston was founded as a small farming and mining village sometime before 1801 when 99 people lived in the village. Maps from 1579 show Johnston as an already established village. The population steadily grew to 600 in 1951 and almost doubled in the next 10 years to 1,133. Since then Johnston has had a steady population growth.
Johnston is not an ethnically diverse village with 99.55% of the population identifying as White. It is also a majority Christian village with 62.4% of people identifying as a Christian, 0.2% as a Buddhist, 0.4% as a Muslim, 0.5 as Other and 26.5% as No Religion. 9.7% of people did not state a religion.
The majority of people, 72.8%, were born in Wales. 23.5% of other people were born elsewhere in the United Kingdom (22% were born in England, 1.3% in Scotland and 0.2% in Northern Ireland). 0.3% were born in Ireland. 1.2% of people were born in countries that were members of the EU before 2001 while 0.4 were born in EU countries that joined after 2001. 1.9% were born in 'other countries'.
59.8% of people identify only as Welsh and 6.7% as Welsh and British. 12.7% identify only as English while 1.2% identify as English and British, 1% identify as English and other. 0.8% identify as Scottish only while 0.2 identify as Scottish and British and 0.2% as Scottish and other. 0.2% identified as only Northern Irish only.
15.5% identify only as British, while 8.7% identify as British and other. 75.8% have no British identity while 32.5 have no Welsh identity, while 1% identify as Welsh and other.
Johnston Community Council, has limited control over aspects of the running of the village.
Johnston CP School is a primary school with year groups, Nursery to Year 6. It has over 150 pupils. In 2017 it moved into a newly built building, previously it had been on its former site for approximately 30–35 years. Before then it was at another site in the north of Johnston.
Pupils in Secondary Education are automatically enrolled in Tasker-Milward V.C. School, in nearby Haverfordwest. Although parents may opt out of this and send their child to another school.
Johnston is served by 9 bus stops, six main with three smaller stops. Buses run to Haverfordwest, Milford Haven, Pembroke, Pembroke Dock, Neyland and Tenby.
Johnston railway station serves as a railway link. Trains run in both directions every 2 hours, with two main termini being Milford Haven railway station and Manchester Piccadilly station. The station itself is unmanned and is a request stop.
Johnston has a wide range of amenities: a petrol station, post office, shop/off licence, doctors' surgery, two car dealership garages, pharmacy, fish & chip shop, Chinese takeaway, three MOT Garages, a play park and a hairdressing salon. there are five pubs, The Vine Inn, The Silverdale, The Railway, The Windsor Hotel and Johnston Country Club.
The Anglican church of St Peter, in the Diocese of St David's and established as a mission church in 1894, became a Chapel of Ease to Saint Paul's Church, Pentre Broughton in 1908. It is a grade II* listed building 
A meetinghouse for The Church of Jesus Christ of Latter-day Saints (LDS Church) was opened in December 2012 and is home to the Milford Haven Branch.
- "Community population 2011". Retrieved 19 April 2015.
- "PENBROK comitat". The British Library. British Library. Retrieved 9 September 2015.
- "GENUKI: Johnston". Retrieved 26 April 2015.
- "Church of St Peter, Johnston". British Listed Buildings. Retrieved 29 December 2013.