The first question is always, how big is a rugby field? To relate it to an American Football field, it is longer and wider.
1 yard = 1.09 meters
A regulation rugby field is 70 meters wide x 100 meters long ( + the In-Goal or Try Zone of 20 meters each end ) , so to convert that, a rugby field is 76.5 yards wide x 109 yards long ( 152.75 yards with try zones )
This makes the rugby pitch approximately the size of a FIFA regulation soccer field.

The next question is always , what do all the lines mean? To help explain a little is a link to a pitch layout and also the meanings of the pitch lines.

It can take years of playing to understand all the intricacies of the pitch, what they mean and when to use certain areas of the pitch to your advantage. This is just a brief explanation to hopefully help clear it up a little.

Enjoy & Cheers!

Rugby Pitch Layout link

Lines going across the Pitch
[b]Halfway Line solid
The halfway line marks the field in half regardless of the size of the field. This line is where the start of game happens, restart after the half, or the kick after a try has been scored.

10 Meter Linedashed
The 10 meter line is marked 10 meters from the halfway line on either side. The 10 meter line marks the distance that a kickoff must go before the opposing team may gain possession of the ball.

22 Meter Line solid
The 22 meter line is measured from the goal line (or try line). This is the line marks the spot play is restarted if the ball is kicked thru the dead ball line. This line also marks the area in which the receiver of a kick for territory ( not a kickoff ) may call mark. In addition a team in possession and behind their own 22 meter line may kick a ball to touch and the opposing team would gain possession of a line-out, at the point that ball crossed the touch line ( side line )

5 Meter Out Line dash hash
There should also be the 5-meter line. These lines are five meters from each goal line. Scrums and lineouts cannot be set closer than the five.

In Goalsolid
The “in goal” is the equivalent of the end zone in football. It is marked by the Goal Line and the Dead Ball Line. The size of the In Goal is not less than 10 meters and not greater than 22 meters. This is often called the Try Zone and is where the player must "touch the ball to ground" in order to score a try ( 5 points )

Dead Ball Line solid
The line at the back of the in goal area (end zone) that designates out of bounds.

Lines going the length of the pitch
Touchline ( Sideline ) solid
The sideline of the field of play. This line defines the difference between in bounds and out of bounds. The touchline itself is considered to be in touch (out of bounds).

5 meterdashed
The five meter line is five meters in field and runs parallel to the touchline ( sideline ). It is the distance that the ball must cross to have the start of a successful lineout

15 meter dashed hash
The fifteen meter line is fifteen meters in-field and parallel to the touch line (sideline). It is the outer limit for a lineout.

The Goal Post
The goal post in Rugby shares the same dimensions as NFL Football. In meters the goal is 5.6 meters wide and 3 meters high at the crossbar.