WW1 (1914-1918) is much more complex than a simple list of causes. While there was a chain of events that led to the fighting, the actual root causes are much deeper and part of a continued debate and discussion.
One of the major causes of WW1 is imperialism. Imperialism is when a country increases its power and wealth through the utilization of additional territories under their control / when colonies are viewed as vital for attaining national wealth and prestige. It is due to this way of thinking resulted in the spreading of old, continental, territorial struggles to a global scale.
Germany was late to join the game of imperialism and due to this, they needed to make up for lost time. Germany entered a state of hyper-imperialism. It is due to this possible shift in European power that Germany had to be contained. France had no issue with this due to the embarrassment that it endured as a result of its defeat during the Franco-Prussian War of 1781 and its desire to re-acquire Alsace and Lorraine.
The increasing competition and desire for greater empires led to an increase in confrontation that helped push the world into WW1. For the most part, imperial conflicts were settled through negotiations. However, in the long run, imperialism created tension between the countries.
The second cause is the complex set of alliance systems, which locked European countries into two (2) rigid, hostile camps. Due to the mutual defense agreements, countries would be pulled into battle, thus, if one country attacked, allied countries were bound to defend them.
The two above-mentioned rigid, hostile camps are referred to as the Triple Alliance (Austria-Hungary, Italy [until 1915] and Germany) and the Triple Entente (France, Russia  and Great Britain).
The third cause of WW1 is that of the arms race / militarism. By the end of the 19th, beginning 20th century, all of the Great Powers of Europe increased military spending drastically. By 1914, Germany had the greatest increase in military buildup. With this, Germany was able to challenge Great Britain’s naval supremacy. Additionally, there had been a great deal of technological advancements in weaponry, such as: new artillery, battleships, airplanes, submarines, etc. The utilization of these new weapons led to bloodier war.
In regard to mobilization plans (Act of War), all countries maintained the belief that this war would be offensive in nature and short in duration. However, the opposite occurred. With the introduction of trench warfare, there is a shift into a dirty, bloody battle. This introduction led to the slaughter of thousands of troops due to the fact that generals maintained the above-mentioned belief in regards to the war.
This can be seen in Germany’s Schlieffen Plan. It was Germany’s plan to knock-out France within six weeks which was the time that Russia would need to mobilize its troops and then move eastward.
The trigger of WW1 is the assassination of Archduke Franz Ferdinand, heir to the Austrian-Hungarian empire on the hands of a Serbian extremist group called the Black Hand. This led to Austria-Hungary declaring war against Serbia. Russia, thinking of itself as the protector of Orthodox Christianity, joined on the Serbian side. Also, with Germany lending its support to Austria-Hungary, France joins on the side of the Serbian–Russian side. Belgium declares its neutrality, which Germany ignores by invading. Great Britain joins this war as a result. This is a domino effect, which is a direct result of the alliance systems.
Due to the Industrial Revolution, you have companies capable of mass production. Governments believed that if they were able to take-over companies / restrict their production so as to focus on military advancement, they would be able to overwhelm the enemy. As a consequence, there was a restriction on human rights as well as on the freedom of industries. However, governments attempted to justify these actions by asserting that this war was unlike any other seen before, it was industrial-based and global in scale. This is one meaning behind the words ‘Total War’.
The other is the removal of able men from the work force so as to send them to the battlefronts. In addition, some countries employed: rationing, government run propaganda, etc.